1) Field of the Invention
The present finding refers to an ophthalmoscopic apparatus.
In particular, the present ophthalmoscopic apparatus falls within the category of apparatuses denominated fundus camera, i.e. it is suitable for vision and photographic reproduction of the eye fundus.
The present ophthalmoscopic apparatus is particularly suitable for vision and/or photographic reproduction of the retina.
Therefore the present invention falls in the optical devices field for eye inspection.
2) Description of Related Art
Nowadays, in the ophthalmoscopic apparatuses field, in particular, an ophthalmoscopic apparatus is known which is equipped with a controlling device employable by the operator to control the distance between the apparatus and the eye to be inspected.
This ophthalmoscopic apparatus comprises also a device for lighting the ocular fundus and a device comprising a detecting screen of ocular fundus image.
Furthermore, this ophthalmoscopic apparatus comprises focusing means for the focusing of ocular fundus on the screen.
In use, the ophthalmoscopic apparatus is placed in front of the eye to be inspected.
In detail, this ophthalmoscopic apparatus comprises a first optical unit and a second optical unit placed in front of the screen and which are aligned each other so to fix a main common optical axis of the ophthalmoscopic apparatus.
The second optical unit is placed between the screen and the first optical unit and is movable along the main optical axis for focusing the ocular fundus image on the screen.
The aforementioned controlling device comprises a luminous indicator placed between the first and the second optical unit and suitable for projecting, through the first optical unit, a luminous radiation towards the eye to be inspected.
The indicator image is reflected from the cornea on the detecting device screen by means of which it can be evaluated by an operator.
The controlling device is structured so that, if this reflected image is clear, then the ophthalmoscopic apparatus is at a right distance from the eye to be inspected, otherwise it is at a wrong distance.
This right distance is that distance where the indicator is conjugated with the eye pupil to be inspected in respect of the first optic unit.
The operator, thus, according to the aforementioned reflected image by the indicator, controls the ophthalmoscopic apparatus distance from the eye so to obtain the aforementioned right distance.
The indicator can consist of an only luminous signal or of a plurality of luminous signals circumferentially placed around the main optical axis.
The offset between such indicators image on the screen and the main optical axis gives the operator information for aligning the ophthalmoscopic apparatus with the eye to be inspected.
In fact, if the ophthalmoscopic apparatus is centred, i.e. is aligned with the eye to be inspected, the optical axis of this latter coincides with the main optical axis.
When the ophthalmoscopic apparatus is placed at the right distance from the eye and is centred on this one, means for focusing are operated which move the second optic unit so to obtain that ocular fundus and screen are conjugated.
Each indicator is realized by a first end of a light guide, in particular an optical fibre, the second end of the latter being in front of a lamp for receiving the luminous radiation.
Alternatively, the indicator can be realized by means of a specular surface on which a luminous radiation generated by a lamp is focused, by a lens, or by an optical unit, having an optical axis transverse to the main optical axis.
The light for lighting the ocular fundus is provided by the lighting device which traditionally comprises, in sequence, a lamp, a lens or an optical unit, and a mask conjugated to the lamp relative to the lens.
The lighting device has a secondary optical axis which intersects the main optical axis.
In correspondence of the intersection between the main and secondary optical axes, a mirror suitable for reflecting the lamp light towards the eye position, along the main optical axis, is placed.
Such mirror is perforated in the middle so as to allow the reflected light by the eye to pass, through the hole, towards the screen.
The mask, of the lighting device, has an annular slit suitable for making an annular beam of light generated by the lamp, such beam strikes peripherally the hole on the mirror.
The mask is conjugated to the eye pupil to be inspected when the ophthalmoscopic apparatus is placed at the aforementioned right distance from the eye, in which case the lamp light lightens the ocular fundus.
The focusing means comprise, further, an emitting device of infrared rays, suitable for lighting the ocular fundus.
The formed on the screen image by infrared light reflected from the ocular fundus, gives instructions for focusing on the screen the ocular fundus.
For the focusing, the second optical unit is moved along the main optical axis in order to have the infrared light image focused on the screen.
The focusing means comprise driving means suitable for jointly moving the second optical unit, along the main optical axis, and the infrared emitting device along the secondary optical axis.
This traditional ophthalmoscopic apparatus is structurally complex in particular because it provides that the lighting device extends transverse to the main optical axis and the infrared emitting device which has to be jointly moved with the second optical unit in order to allow the ocular fundus focusing.
A further reason of structural complexity is provided by the foreseen means for generating the indicator.
In fact the light guides, i.e. optical fibres, use requires a manual assembling and use of skilled operators to detriment to an easy and cheap production.
The known solution, in alternative to light guides, i.e. the lamp-lens-mirror unit, determines a size transversally to the main optical axis and the need of retaining such unit components each other correctly positioned.
Such structural complexity determines this traditional ophthalmoscopic apparatus to be complex to produce and also the maintenance of the same is complex, to detriment to its inexpensiveness.
The underlying problem of the present invention is to simplify this traditional ophthalmoscopic apparatus structure.
Main task of the present finding is of realizing an ophthalmoscopic apparatus that gives such problem a solution solving the before disclosed complained drawbacks of the ophthalmoscopic apparatus.
Into the scope of such task is an aim of the present finding to propose an ophthalmoscopic apparatus which, in comparison with the traditional one, has a less size in the transverse direction relative to the main optical axis.
Another aim of the present finding consists in realizing an ophthalmoscopic apparatus which uses fewer optical components, i.e. lenses or optical units, in comparison with the disclosed traditional ophthalmoscopic apparatus.
A further aim of the present finding consists in proposing an ophthalmoscopic apparatus which is of easier maintenance in comparison with the above disclosed traditional ophthalmoscopic apparatus.